APPLICATION OF POTENTIOSTATIC MEASUREMENTS ACCORDING TO PN-EN 480-14 IN ASSESSMENT OF THE EFFICIENCY OF REINFORCEMENT PROTECTION AGAINST CORROSION BY CONCRETE WITH ADDITION OF FLY ASHES

S t r e s z c z e n i e Zastąpienie części cementu w betonie popiołami lotnymi – produktami spalania paliw stałych, wymaga przeprowadzania badań, w tym stopnia ochrony zbrojenia przed korozją, którą powinien zapewnić beton. W artykule przedstawiono porównanie wyników badań skuteczności ochrony antykorozyjnej betonu z cementu z dodatkiem wapiennych popiołów lotnych względem stali zbrojeniowej. Badania przeprowadzono metodami elektrochemicznymi. Wyniki uzyskane za pomocą pomiaru potencjostatycznego na wkładkach zbrojeniowych umieszczonych w próbkach cylindrycznych zgodnie z normą EN 480-14 porównano z badaniami postępu korozji zbrojenia wywołanej chlorkami w obciążonych i zarysowanych elementach próbnych wykonanych z tych betonów. Badania elementów zarysowanych odzwierciedlają zachowanie konstrukcji żelbetowej podczas pracy w niekorzystnych warunkach środowiskowych, charskteryzowanych jako klasy ekspozycji XD i XS. Porównanie badań wskazuje na możliwość zastosowania pomiaru potencjostatycznego do bieżącej oceny właściwości ochronnych betonu z dodatkami mineralnymi. K e y w o r d s : Electrochemical tests; High calcium fly ash; Potentiostatic measurements; Protective properties of concrete; Reinforcement corrosion. 3/2017 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 109 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T The Si les ian Univers i ty of Technology No. 3/2017 K . D o m a g a ł a , A . Ś l i w k a of concrete. Replacing part of the cement in the concrete with fly ash requires testing, including the degree of the reinforcement protection against corrosion provided by concrete. Determination of these characteristics allows for predicting the durability of reinforced concrete structures made from materials modified with coal combustion products. The results of published studies are not directly comparable due to the different types of ash used and the percentage of cement used as well as the different concrete recipes, curing conditions, and the way the experiment is conducted. Most of the results confirmed that the use of ashes in appropriate proportions does not impair the protective properties of concrete to reinforcing steel [1, 2, 3, 4, 5] and improves the tightness of concrete [4, 6]. In some studies conducted in the environment heavily contaminated with carbon dioxide and chlorides, accelerated corrosion of reinforcement by the introduction of silica fly ash replacing part of the cement was found [3, 7, 8]. In addition, the use of common building chemicals poses a risk of antagonistic action and, as a consequence, deterioration of protective properties to reinforcing steel. Composition of fly-ashes can also vary considerably depending on the source and fuel used. Due to this should be conducted current control of protective properties. In the case of control tests, the speed of obtaining results is important. Potentiostatic test according to PN-EN 480-14 allows for fast results, but test conditions deviate from the natural conditions in which the construction works. This can have an impact on the proper reasoning about proper protection in real construction. It should answer the question whether these tests are reliable and can be to draw conclusions about the protective properties of concrete containing fly ash cement. Therefore, in order to verify the protective properties of concretes containing fly ash cements were examined [9]. Rapid selection tests were performed on standard test elements according to standard [10]. Then corrosion rate of reinforcing steel caused by the impact of a 3% solution of sodium chloride on reinforced beam elements was determined by linear polarization. Samples for both tests were made of concrete on cement with different contents of high calcium fly ash (Tab. 1). Concrete test elements made of Portland cement were also tested, which were reference level during the study. 2. CORROSION SUSCEPTIBILITY OF THE REINFORCEMENT IN CONCRETE – POTENTIOSTATIC TESTS 2.1. Technique of potentiostatic tests Specimens for potentiostatic tests were prepared in accordance with PN-EN 480-14 in the form of cylin110 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 3/2017 Figure 1. Potentiostatic measurements: a) the test element scheme: 1 – working electrode (reinforcing bar), 2 – concrete, 3 – protective coating of plastic, b) photography of test elements Table 1. Types of cement towards electrochemical measurements used in the experiments Series Cement High calcium fly ash [% by weight]